Question

Why doesn't the IDL pass through land?

Answer 1

IDL doesn't pass that the land to prevent distributing to places of the same region or continent or more specifically a country into two different time zones hence it does not pass thru the land

Answer 2

If IDL had passed through the land part of some country, it would have led to confusion of two different dates and days in the same country. Besides, been an imaginary line it would have been difficult to track when and where exactly the ideal has been crossed. Hence, to avoid the confusion international date line was drawn in such a way that it will pass through only the Pacific Ocean.